I left Hawaii to visit Alaska for 4 days, got back, and my 4-year old car battery was dead. It would not take a charge, but could be jumped, however, now it had to be repeatedly jumped. The alternator was fine. Why would being going for just a short time simply kill my battery? I simply forgot to unhook the cables. I purchased a new battery and it runs like a charm. Why does not starting the car result in such a drastic outcome? I remember growing up that if the battery died, it could be brought back to life with a jump and that was all it needed.
Your battery gave up because it was at it’s end of life. Simple as that. Some seem to last forever and I have had some that just did not last. A good battery will be fine for four days . I have let one vehicle set for 3 weeks and it started just fine.
Batteries do not live forever.
There are responders on this site that will keep their batteries until they die.
Others, like myself, replace them when 3-5 years old.
I just had a battery fail at 18 months-replaced free under warranty.
My 82 Dodge truck that I use to have, the battery in it would hold a charge for 6 months or more, only drove it a couple times a year, never had to jump/charge it, But then I also had a huge marine dual purpose battery in it.